Torque indicating wrench

ABSTRACT

A HEX KEY WRENCH IS PROVIDED WITH A TORQUE INDICATING DEVICE WHICH IS ATTACHED TO THE BOLT ENGAGING LEG OF THE WRENCH AND HAS AN INDICATING ARM POSITIONED TO LIE ALONG THE OTHER LEG OF THE WRENCH. WHEN TIGHTENING TORQUE IS APPLIED TO THE BOLT, THE NON-ENGAGING LEG DEFLECTS SLIGHTLY AND, SINCE THE INDICATING ARM REMAINS SUBSTANTIALLY STATIONARY, THE RELATIVE MOVEMENT BETWEEN THEM PROVIDES A VISUAL INDICATION OF THE MAGNITUDE OF THE TORQUE APPLIED.

' Jan. 19, 1971 w. J. BU$CH.'JR

' TORQUE INDICATING WRENCH Filed April 4., 1968 INVENTOR. WILLIAM J. BUSCH Jr.

ATTORNEYS United States Patent 3,555,938 TORQUE INDICATIN G WRENCH William J. Busch, Jr., Warminster, Pa., assignor to Standard Pressed Steel Co., Jenkintown, Pa., a corporation of Pennnsylvania Filed Apr. 4, 1968, Ser. No. 718,745

Int. Cl. B25b US. Cl. 8152.4 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to torque indicating wrenches and more in particular to torque indicating lwrenches used as a production tool wherein the tool is designed to apply uniformly a predetermined tightening torque to fastening elements such as hex head screws or bolts, socket head screws, and the like.

In production line applications where the line is set up to mass produce a product and where socket head screws or bolts or the like are used as the fastening element, the screws or bolts should ideally be seated with the same tightening torque. In many instances it is imperative that the recommended tightening torque for the bolt be applied to induce the specified design load in order to have the product function in the proper manner. In addition, if the bolt is over torqued there is the possibilty that the bolt itself will snap, or the product will be brinelled or deformed in some manner and if insuflicient torque is applied, the fastening element will not be tight enough to prevent the fastening element from working loose during use of the product.

A torque Wench can of couse be used to obviate the problem of improper seating torque. Torque wrenches that have been used heretofoe have a dial indicator associated with the wrench on which the magnitude of the applied torque, in inch-pounds or foot-pounds, can be read directly. These torque wrenches are designed for a wide range of uses and can apply any desired tightening torque within a specified range. Consequently, they are relatively expensive, usually large and cumbersome to use, are subject to damage and miscali-bration when dropped or otherwise subjected to high impact stresses, and, in general, are not feasible for production line use where the range of applicable use is limited, most often to a single value of applied tightening torque. Additionally, since the torque must be read on the dial indicator while the operator is applying the torque, there is a tendency to apply the torque slowly and carefully while watching the dial indicator which adds considerably to production time.

In accordance with a preferred embodiment of the present invention, a torque indicating wrench is pro videl which comprises an L-shaped hex key having one leg adapted to engage the socket of a socket head screw and a snap-on indicating arm mounted on the engaging leg which is spaced from and overlies, the torque applying leg or handle of the wrench. As torque is applied to the bolt, the handle deflects and, since the indicating arm is affixed to the engaging leg and is spaced from the handle,

the indicating arm remains stationary. Thus, the wrench Patented Jan. 19, 1971 handle, as it deflects, traverses across the tip of the indicating arm. This relative movement is visible to the operator and, as it is proportional to the torque applied to the bolt, may be used to indicate a predetermined value of tightening torque.

The construction of such a preferred embodiment as well as the advantages thereof, which include simplicity of design and economy of manufacture, ready adaptability to rapid production line applications, relative ease in changing indicating arms to increase versatility in order to indicate varying torques, and simplicity of use, IWill become further apparent from the following specification when considered in conjunction with the accompanying drawing wherein:

FIG. 1 is a perspective view showing the torque indicating wrench of the present invention in engagement with a socket head screw;

'FIG. 2 is a plan view showing the deflection of the wrench handle; and

FIG. 3 is a sectional view taken on line 33 of FIG. 2.

With reference to the drawing, a hex key 10 having an engaging leg 12 and a handle 14 is shown positioned in a socket head bolt or screw 16 which is threadably received in a work piece 18. An indicating arm 20 is affixed to the engaging leg 12 of the key 10 by a hexshaped spring clip 22, although it may be aflixed in any manner such as by welding or bonding. The important consideration for attaching the indicating arm is that relative movement is precluded between the arm 20 and that portion of leg 12 to which the indicating arm is attached. The indicating arm 2.4 is spaced slightly from, and is coextensive with, the handle portion 14 of the key.

To engage the screw 16 in work piece 18, the engaging leg 12 is inserted into socket 25 of the screw and torque is applied to the hex key 10, usually by grasping the handle 14 and turning the hex key. The handle portion 14 will deflect, as shown in FIGS. 2 and 3 when the screw is seated and tightening torque is applied. The indicating arm, since it is aflixed to the key only on the engaging leg portion 12, will rotate with the hex key as the hex key is rotated until the screw is seated but the arm 24 will not deflect as does the handle 14 when the tightening torque is applied. Thus, there will be a relative movement between the handle portion 14 and the indicating tip 26 of the indicating arm 24. The relative movement of the arm 14 to the tip 26 is proportional to and indicative of the applied torque.

For a particular application, the desired tightening torque for the bolt or screw is determined and the length of the indicating arm is chosen so that when the handle 14 deflects under the predetermined applied torque the movement of the handle 14 relative to the indicating tip 26, or scribed indications 2-8 on the handle, will represent the predetermined value of applied torque.

The torque that is indicated can be varied by selecting indicating arms of different lengths. If the arm is short in relation to the handle 14 there is less relative deflection at the indicating tip 26, and, therefore, it will require the application of a higher torque to provide sulficient deflection to cause the indicating tip 26 to traverse the full width of the top of the handle. As the indicating arm 24 is made longer, the deflection of the handle relative to the tip 26 of the indicating arm becomes greater, allowing the tip 26 fully to traverse the top of the handle with less applied torque.

It is thus seen an operator using the indicating torque wrench can uniformly apply the same tightening torque in a production operation by applying a tightening torque until the indicating tip 26 traverses the selected distance on the wrench handle 14.

I claim:

1. A torque indicating wrench assembly comprising:

a wrench formed of bar stock having a polygonal crosssection bent into a generally L-shape to form a first leg portion and a second leg portion, said first leg portion being adapted to engage a fastening element and said second leg portion being adapted to receive the applied tightening torque, said second leg portion having a flat top surface including a pair of edges; and,

a generally L-shaped indicator member including a support arm attached to said first leg portion and an indicator arm overlying said fiat top surface of said second leg portion, said indicator arm terminating at a point intermediate of said top flat surface, whereby upon the application of a tightening torque said second leg portion will deflect relative to said indicating arm with the magnitude of said relative movement being indicative of the applied tightening torque.

2. A torque indicating wrench assembly in accordance with claim 1 wherein said support arm is attached to said first leg by means of a spring clip member, said spring clip member having a polygonal shape thereby to hold said indicator arm securely on said wrench and preclude relative movement between said indicating arm and said first leg portion.

3. A torque indicating wrench assembly in accordance with claim 1 wherein said support arm is bonded to said first leg portion to hold said indicating arm securely on said wrench and preclude relative movement between said indicating arm and said first leg portion.

4. A torque indicating assembly in accordance with claim 1 wherein said fiat top surface includes scribed indentations adjacent said point where said indicator arm terminates.

References Cited UNITED STATES PATENTS 3,076,362 2/1963 Able 81--52.43 3,283,620 11/1966 Bailey 8142.43

FOREIGN PATENTS 985,565 3/1951 France.

JAMES L. JONES, 111., Primary Examiner U.S. Cl. X.R. 73-139 

